Survey of Capabilities and Applications of Accurate Clocks: Directions for Planetary Science

Déhant, V.; Park, Ryan; Dirkx, Dominic; Iess, L.; Neumann, Gregory A.; Turyshev, Slava G.; Hoolst, Tim Van

doi:10.1007/978-94-024-1566-7_9

Cited by 3 publications

(4 citation statements)

References 45 publications

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“…Future extension of the Apollo seismometer network with a better coverage (Mimoun et al, ) would allow a better determination of ρ c and

R_{CMB}

thereby improving current LLR estimations. With advancements in the LLR measurement (Adelberger et al, ; Courde et al, ) continuing to accumulate high‐accuracy data sets and emerging observational techniques (Dehant et al, ), future LLR analysis will allow unprecedented access to the dynamical nature of the lunar interior. Moreover, the methods described here can be applied to study the influence of the liquid core on the rotation of other planets such as Mars (Folkner et al, ).…”

Section: Discussionmentioning

confidence: 99%

Observational Constraint on the Radius and Oblateness of the Lunar Core‐Mantle Boundary

Viswanathan

Rambaux

Fienga

et al. 2019

Geophysical Research Letters

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Lunar laser ranging (LLR) data and Apollo seismic data analyses, revealed independent evidence for the presence of a fluid lunar core. However, the size of the lunar fluid core remained uncertain by ±55 km (encompassing two contrasting 2011 Apollo seismic data analyses). Here we show that a new description of the lunar interior's dynamical model provides a determination of the radius and geometry of the lunar core‐mantle boundary (CMB) from the LLR observations. We compare the present‐day lunar core oblateness obtained from LLR analysis with the expected hydrostatic model values, over a range of previously expected CMB radii. The findings suggest a core oblateness (fc=(2.2±0.6)×10−4) that satisfies the assumption of hydrostatic equilibrium over a tight range of lunar CMB radii ( RCMB=381±12 km). Our estimates of a presently relaxed lunar CMB translates to a core mass fraction in the range of 1.59–1.77% with a present‐day free core nutation within (367±100) years.

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“…Future extension of the Apollo seismometer network with a better coverage (Mimoun et al, ) would allow a better determination of ρ c and

R_{CMB}

Section: Discussionmentioning

confidence: 99%

Observational Constraint on the Radius and Oblateness of the Lunar Core‐Mantle Boundary

Viswanathan

Rambaux

Fienga

et al. 2019

Geophysical Research Letters

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“…A stability of about 10 −15 over a typical ILR light time of 1000 s will result in 1 ps timing error (0.3 mm one-way range error), and is achievable by H-masers (e.g. Dehant et al, 2017). For the space segment, stability is only required over the time δt, putting sub-mm errors well within the capabilities of present spaceborne systems.…”

Section: Measurement Errorsmentioning

confidence: 97%

Laser and radio tracking for planetary science missions—a comparison

Dirkx

Procházka

Bauer

et al. 2018

J Geod

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At present, tracking data for planetary missions largely consists of radio observables: range-rate (Doppler), range and angular position (VLBI/ DOR). Future planetary missions may use Interplanetary Laser Ranging (ILR) as a tracking observable. Two-way ILR will provide range data that are about 2 orders of magnitude more accurate than radio-based range data. ILR does not produce Doppler data, however. In this article, we compare the relative strength of radio Doppler and laser range data for the retrieval of parameters of interest in planetary missions, to clarify and quantify the science case of ILR, with a focus on geodetic observables. We first provide an overview of the near-term attainable quality of ILR, in terms of both the realization of the observable and the models used to process the measurements. Subsequently, we analyse the sensitivity of radio Doppler and laser range measurements in representative mission scenarios for parameters of interest. We use both an analytical approximation and numerical analyses of the relative sensitivity of ILR and radio Doppler observables for more general cases. We show that mm-precise range normal points are feasible for ILR, but mm-level accuracy and stability in the full analysis chain are unlikely to be attained, due to a combination of instrumental and model errors. We find that ILR has the potential for superior performance in observing signatures in the data with a characteristic period of greater than 0.33-1.65 hours (assuming 2-10 mm uncertainty for range and 10 µm/s at 60 s for Doppler). This indicates that Doppler tracking will typically remain the method of choice for gravity field determination and spacecraft orbit determination in planetary missions. ILR data will be able to supplement the orbiter tracking data used for the estimation of parameters with a once-per-orbit signal. Laser ranging data, however, are shown to have a significant advantage for the retrieval of rotational and tidal characteristics from landers. Similarly, laser ranging data will be superior for the construction of planetary ephemerides and the improvement of solar system tests of gravitation, both for orbiter and for lander missions.

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“…For the robust analysis of tracking data from planetary missions, the dynamics of solar system bodies under investigation should ideally be modelled to well below the observational accuracy and precision. Several exceptionally accurate tracking-data types are emerging for planetary missions, such as multiwavelength radiometric range and Doppler measurements (Dehant et al, 2017), same-beam interferometry (SBI) (Kikuchi et al, 2009;Gregnanin et al, 2012), and interplanetary laser ranging (ILR) (Degnan, 2002;Turyshev et al, 2010;Dirkx, 2015). For the analysis of these data, dynamical models for natural bodies need to be developed and implemented to beyond the current state-of-the-art of typical state propagation and estimation software.…”

Section: Introductionmentioning

confidence: 99%

“…Currently, the dynamical models of planetary/asteroid systems that are used in typical state propagation and estimation software cannot robustly capture the motion to the measurement accuracies of ILR and SBI (e.g., Dirkx, 2015;Dehant et al, 2017), which would prevent the data from being optimally exploited. Among others, characterizing such systems' dynamics will require a new level of detail for the models used to describe the gravitational interaction between extended bodies.…”

Section: Introductionmentioning

confidence: 99%

Propagation and estimation of the dynamical behaviour of gravitationally interacting rigid bodies

Dirkx

Mooij

Root

2019

Astrophys Space Sci

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Next-generation planetary tracking methods, such as interplanetary laser ranging (ILR) and same-beam interferometry (SBI) promise an orders-of-magnitude increase in the accuracy of measurements of solar system dynamics. This requires a reconsideration of modelling strategies for the translational and rotational dynamics of natural bodies, to ensure that model errors are well below the measurement uncertainties.The influence of the gravitational interaction of the full mass distributions of celestial bodies, the so-called figure-figure effects, will need to be included for selected future missions. The mathematical formulation of this problem to arbitrary degree is often provided in an elegant and compact manner that is not trivially relatable to the formulation used in space geodesy and ephemeris generation. This complicates the robust implementation of such a model in operational software packages. We formulate the problem in a manner that is directly compatible with the implementation used in typical dynamical modelling codes: in terms of spherical harmonic coefficients and Legendre polynomials. An analytical formulation for the associated variational equations for both translational and rotational motion is derived.We apply our methodology to both Phobos and the KW4 binary asteroid system, to analyze the influence of figure-figure effects during estimation from next-generation tracking data. For the case of Phobos, omitting these effects during estimation results in relative errors of 0.42% and 0.065% for theC 20 andC 22 spherical harmonic gravity field coefficients, respectively. These values are below current uncertainties, but orders of magnitude larger than those obtained from past simulations for accurate tracking of a future Phobos lander, showing the need to apply the methodology outlined in this manuscript for selected future missions.

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Survey of Capabilities and Applications of Accurate Clocks: Directions for Planetary Science

Cited by 3 publications

References 45 publications

Observational Constraint on the Radius and Oblateness of the Lunar Core‐Mantle Boundary

Observational Constraint on the Radius and Oblateness of the Lunar Core‐Mantle Boundary

Laser and radio tracking for planetary science missions—a comparison

Propagation and estimation of the dynamical behaviour of gravitationally interacting rigid bodies

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